As described in 3GPP TS25.401, in a CN (Core Network) domain, there are CS domain, PS (Packet Switched) domain, and BC (Broadcast) domain.
The 3GPP TS25.331 sets forth a technique for regulating domain access to the CS and PS domains, which are CN domains. The CS domain refers to a CN domain which handles circuit-switched services for such data as audio and UDI (Unrestricted Digital Information). The PS domain refers to a CN domain that mainly handles packet-switched services.
In a conventional practice, when a base station control apparatus (RNC Radio Network Controller) regulates access to the CN domain by a mobile terminal, it informs the mobile terminal of System Information Block Type 3 of RRC (Radio Resource Control) protocol (see Patent Documents 1 and 2, for instance).
In such a case, since a mobile terminal when idle or a mobile terminal that uses a common channel (Cell_FACH, Cell_PCH, and URA_PCH) can read in the System Information Block Type 3 informed by the base station control apparatus, the mobile terminal autonomously regulates its access to the CN domain based on the System Information Block Type 3.
More specifically, a mobile terminal in an idle state or a mobile terminal using a common channel saves access class regulation patterns that are set in the System Information Block Type 3, and autonomously regulates its access to the CN domain when it determines that the mobile terminal is now covered by domain access regulation based on an access class regulation pattern.
However, a mobile terminal that is performing packet communication using an individual channel (Cell_DCH) cannot read in the System Information Block Type 3. For this reason, a related base station control apparatus cannot impose regulation of domain access to the CN domain on a mobile terminal that is currently conducting packet communication over an individual channel.
By way of example, consider a case where access to the CS domain for the purpose of voice calling are regulated and access to the PS domain for packet communication are allowed to continue when the CN is in congestion due to signaling, e.g., for voice calling.
In such a situation, since a mobile terminal that is performing packet communication using an individual channel cannot be covered by regulation of domain access to the CS domain as described above, such a mobile terminal transmits an INITIAL DIRECT TRANSFER message, which is a message for establishing a signaling connection, in order to establish a signaling connection to the CS domain.
In response, the base station control apparatus blocks the INITIAL DIRECT TRANSFER message and sends a SIGNALING CONNECTION RELEASE message back to the mobile terminal. In such a manner, the base station control apparatus releases a signaling connection to the CS domain and prevents establishment of a signaling connection.
However, the base station control apparatus cannot prevent a mobile terminal from voice re-calling such as by redialing. Accordingly, repeated voice calls may bring the base station control apparatus and/or an exchange into an overloaded state.
Patent Document 1: Japanese Patent Laid-Open No. 09-009340
Patent Document 2: Japanese Patent Laid-Open No. 2003-244284
In view of such circumstances, it is an object of the present invention to provide a base station control apparatus and a domain access regulation method that can impose regulation of domain access to the CS domain even on a mobile terminal that is performing packet communication using an individual channel.